Secondary battery positive electrode, and secondary battery

Abstract

This secondary battery positive electrode is provided with a positive-electrode current collector, a positive-electrode mixture layer, and an intermediate layer disposed between the positive-electrode current collector and the positive-electrode mixture layer. The intermediate layer comprises: a first intermediate layer that includes a non-oxide conductive inorganic compound and a positive-electrode active material; and a second intermediate layer that includes an insulating inorganic material and a non-oxide conductive inorganic compound. The conductive inorganic compound becomes an insulating oxide at 300° C. or above.

The invention claimed is: 
     
       1. A positive electrode for a secondary battery, comprising:
 a positive electrode current collector; 
 a positive electrode mixture layer; and 
 an intermediate layer disposed between the positive electrode current collector and the positive electrode mixture layer, wherein 
 the intermediate layer consists essentially of a mixture of an inorganic compound, a positive electrode active material, and a binder, 
 the inorganic compound remains an electrically conductive nonoxide at a temperature less than 300° C. and becomes an insulating oxide at 300° C. or more, 
 the positive electrode mixture layer includes a positive electrode active material, a binder, and a conductive agent that is different from the electrically conductive nonoxide, 
 wherein a content of the inorganic compound in the intermediate layer is within a range of 0.1 mass % to 20 mass %, and wherein the intermediate layer further includes an insulating inorganic material that includes at least one of the group consisting of aluminum oxide, titanium oxide, zirconium oxide, silicon oxide, manganese oxide, magnesium oxide, nickel oxide, boron nitride, aluminum nitride, magnesium nitride, silicon nitride, aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, aluminum hydroxide, boehmite, and Ni— Cu—Zn ferrite. 
 
     
     
       2. The positive electrode for a secondary battery according to  claim 1 , wherein the inorganic compound becomes the insulating oxide at a temperature of 300° C. or more and 500° C. or less. 
     
     
       3. The positive electrode for a secondary battery according to  claim 1 , wherein the inorganic compound includes at least one of the group consisting of TiC, ZrC, HfC, VC, NbC, TaC, WC, TiN, ZrN, HfN, VN, NbN, TaN, TiB 2 , ZrB 2  HfB 2 , VB 2 , NbB 2 , TaB 2 , W 2 B 5 , Mo 2 B 5 , FeB, NiB, TiSi 2 , ZrSi 2 , CrSi 2 , VSi 2 , NbSi 2 , TaSi 2 , WSi 2 , and MoSi 2 . 
     
     
       4. The positive electrode for a secondary battery according to  claim 1 , wherein a thickness of the intermediate layer is one half or less of a thickness of the positive electrode mixture layer. 
     
     
       5. A secondary battery including:
 the positive electrode according to  claim 1 ; 
 a negative electrode; and 
 an electrolyte. 
 
     
     
       6. The positive electrode for a secondary battery according to  claim 1 , wherein a content of the positive electrode active material in the intermediate layer is within a range of 80 mass % to 99.9 mass %. 
     
     
       7. The positive electrode for a secondary battery according to  claim 1 , wherein the positive electrode active material included in the intermediate layer is the same material as the positive electrode active material included in the positive electrode mixture layer. 
     
     
       8. The positive electrode for a secondary battery according to  claim 1 , wherein the positive electrode active material included in the intermediate layer is a different material from the positive electrode active material included in the positive electrode mixture layer. 
     
     
       9. The positive electrode for a secondary battery according to  claim 1 , wherein a thickness of the intermediate layer is 1/150 or more and one half or less of a thickness of the positive electrode mixture layer. 
     
     
       10. The positive electrode for a secondary battery according to  claim 1 , wherein a content of the binder in the intermediate layer is 0.1 mass % to 5 mass %.